1. Field of the Invention
The present invention relates to image quality improvement in the field of video processing. More particularly, the present invention can be applied to image quality improvement in end consumer products like television, display sets, video CD players, DVD players or recorders and set-top-boxes.
2. Description of the Related Art
Basic peaking for improvement in video image quality typically comprises a user-defined peaking frequency and combinations of frequency and filter type that can be set differently according to user-preference or profile settings.
More advanced peaking uses a peaking filter in combination with the re-scaling, for example a peaked frequency response on a rescaling polyphase filter. In that case, the absolute frequency of the filter changes with the resizing ratio to guarantee that the same details are peaked during zoom in or zoom out applications. Similar to basic peaking, a user-defined peaking frequency is selected among pre-determined filter responses with consideration of the scaling factor.
The frequency characteristics of input video are dependent on local video content and they may be subjected to different processes of attenuation and bandwidth limitation prior to peaking. Examples of processes that affect frequencies of video include source capture or generation, camera zoom-in and out, source format and corresponding display format, transmission bitrate, transmission bandwidth and video editing, video pre-processing and post-processing.
Prior art solutions can compensate for change in bandwidth only under specific scenarios where the video resizing is performed in combination with peaking to convert the source format to an output display format. However, an application of peaking in a backend TV chip must be robust to input with any frequency content.
Effective sharpness enhancement may be achieved with peaking at critical frequencies specific to the video content. Peaking at a frequency lower than the critical range makes the picture un-natural with large halos surrounding the large object edge. Peaking at a frequency above the critical range may result in insufficient sharpness and amplification of noise.
A prior art circuit is shown in FIG. 3 including an input video, a peaking filter 302, a user peaking gain input, an adder, and a peaked video output.
What is desired, therefore, is a simple global automatic frequency selection circuit and method so that optimal sharpness enhancement may be achieved.